EP1430983B1 - Method for electrochemical shaping - Google Patents

Description

The invention relates to a method for shaping complicated shaped components, in particular wheels with integrally molded blades for turbomachines, by means of electrochemical ablation.

In integrally formed, molded from the solid material impellers for blowers, compressors and turbines, for example, designed in Bliskbauweise impellers of jet engines, the formation of curved in complex 3D geometry blades is known to be made by cutting shaping with a milling tool. Due to the strong curvature of the blades and the complicated gap shape between the blades, their geometries can no longer be produced in contact with the flanks. Therefore, the shaping is possible only in point contact. This process is extremely time-consuming and costly and therefore only of limited suitability for mass production of, for example, blisk-type compressor disks. In addition, after the milling process additional processing of the profiled surface due to the point milling in a grinding process is required.

Also, the repair of an impeller in which damaged blades or blade parts replaced or repaired by chill welding, build-up welding and the like be required, requires a costly post-processing of the repaired blade.

A well-known shaping method by material removal, as for example in the DE 29 03 873 is based on an electrochemical machining of the workpiece, in which a correspondingly shaped electrode oscillates at a short distance linearly above the surface acted upon by an electrolyte surface and with a linear feed of the electrode removes the material according to the electrode shape. The electrochemical removal of the material is carried out by the so-called ECM method (electro-chemical machining) and the PEM method (precise electro-chemical machining) in such a way that the linear oscillation exporting electrode at the time of the smallest distance from the machined, With an electrolyte surrounded workpiece is subjected to a voltage pulse. The advanced PEM process, in which no electrode wear and no thermal influence on the workpiece to be machined, is characterized by high machining accuracy and surface quality.

In the US 4,999,093 The use of the known advantageous electrochemical shaping in the production of turbine blades or other components with a three-dimensionally curved shape has already been proposed. However, because of the three-dimensionally curved, complicated shape of the gap to be formed in each case between two adjacent blades, the device described therein is not suitable for producing impellers made in one piece, for example of blisk construction, with blades formed from the solid material.

From the EP 0 292 213 A1 , which is to be regarded as the closest prior art, a method for producing a blade-equipped disc by electrochemical machining is known in which the opposite blade surfaces are respectively processed with first and second electrodes, wherein during processing, the first and second electrodes in Move and rotate the direction of the blade surfaces and the relevant blade of the disc is moved in the direction of the electrodes. By a rotational movement of the workpiece, a subsequent blade blank is aligned with the electrodes in order subsequently to produce the blade in the manner described above on the circumference of the disc by electrochemical machining.

The invention has for its object to provide a method for electrochemical machining of workpieces, can be manufactured or repaired with a low workload with the complicated shaped components, in particular integrally formed wheels with molded from the solid material curved blades for fluid flow machines.

According to the invention the object is achieved by a method according to the features of patent claim 1.

From the dependent claims, further features and advantageous developments of the invention.

The basic idea of the method according to the invention for the electrochemical machining of workpieces is that a circular oscillation of the electrode or of the workpiece takes place synchronously with the linear oscillation of the electrode or of the workpiece, so that a complicatedly shaped electrode, for example in the form of a Three-dimensionally curved compressor blade, with a very small material removal in the workpiece to be machined can screw in, as it were. Further shaping up to the exact gap width and blade shape takes place without further linear oscillation only by subsequent circular oscillation in conjunction with a circular feed in one direction and / or the other direction of rotation. In this way, it is possible, complicated shaped structures, for example, integrally molded, three-dimensionally curved blades and thus made of one piece turbine impellers (so-called. Bliskscheiben) by electrochemical machining in the highest accuracy and surface quality as well as stress-free manufacture or repair, so that at the required process for the production of blisk discs required rework for surface smoothing is eliminated and the manufacturing and repair costs are substantially reduced.

Another important feature of the invention, for example in the manufacture of compressor blade wheels, is that by using the above method with a conventionally produced sample workpiece used as an electrode, electrochemical machining produces a workpiece negative electrode functioning as a working electrode in the further process is initially sunk only in a blank and finally forms the blades in the subsequent circular oscillation.

The synchronous linear and circular movements can be carried out both by the electrode (electrode holder) and by the workpiece to be machined (workpiece holder) or else by the workpiece and the electrode.

In mass production of compressor wheels, the electrode preferably performs the linear movements and the workpiece preferably performs the circular movements.

The method can also be used to advantage in the repair of compressor disks or compressor disk drums. In this case, the rotational movement, that is, the circular oscillation and the circular feed of the disc or drum takes place about an axis perpendicular to the linear movement of the electrode. In addition, the electrode is displaceable in the X and Y axes.

Fig. 1 bis 8

eine vereinfachte schematische Darstellung der einzelnen erfindungsgemäßen Verfahrensschritte zur Herstellung des Schaufelkranzes eines Verdichterlaufrades, wobei in der Zeichnung jeweils nur ein bestimmter Sektor des Werkzeugs und des Werkstücks bzw. Schaufelkranzes in Abwicklung wiedergegeben ist;

Fig. 9

eine schematisierte Ansicht einer Vorrichtung mit überlagerter Zirkularoszillation/-vorschub um eine vertikale Achse zur Herstellung kompliziert geformter Bauteile durch elektro-chemisches Abtragen von Werkstoff nach dem PEM-Verfahren; und

Fig. 10

eine Darstellung der Vorrichtung nach Fig. 9, jedoch mit Zirkularoszillation/-vorschub um eine horizontale Achse.

An embodiment of the invention will be explained in more detail with reference to the drawing. Show it:

Fig. 1 to 8

a simplified schematic representation of the individual process steps according to the invention for the production of the blade ring of a compressor impeller, wherein in the drawing only a particular sector of the tool and the workpiece or blade ring is reproduced in settlement;

Fig. 9

a schematic view of a device with superimposed circular oscillation / feed about a vertical axis for the production of complicated shaped components by electrochemical removal of material by the PEM process; and

Fig. 10

a representation of the device according to Fig. 9 , but with circular oscillation / feed about a horizontal axis.

To Druchführung the method, for example, a device according to Fig. 9 used, comprising a formed of a base 1, side walls 2 and a cross member 3 machine housing 4. On the base 1 is a workpiece holder 5, that is, a work table on which a workpiece to be machined (not shown) is held during operation of the device. The work table / the workpiece holder 5 is associated with a torsional vibration drive 6 (first drive member) to put the work table 5 and thus the workpiece to be machined about a vertical center axis in a circular _oscillation (circular _oscillation , arrow C _osz ). Another, connected to the torsional vibration drive 6 rotary feed drive 7 (second drive member) ensures simultaneously with the circular vibration a linear horizontal rotational feed movement (arrow C _before ) the workpiece holder 5 in opposite directions.

On the machine gantry 3, a tool carriage 8, which is displaceably mounted on it in accordance with the double arrow X, is arranged with electrode holder 9. The linearly guided in the tool carriage 8 electrode holder 9 can perform a linear oscillation (linear oscillation, double arrow Z _osz ) and a linear vibration superimposed linear vertical feed movement (double arrow Z _before ) and is for this purpose also with a (third and fourth) drive 10 connected for the linear feed motion and the linear swinging motion. The horizontal feed movement of the tool carriage 8 causes a fifth drive.

The function of the apparatus described above and the method according to the invention carried out with the aid of the invention will be described below using the example of the production of an integrally formed compressor impeller (blisk disk of an engine) on the basis of FIGS. 1 to 8 explains:

First, in a first method step, a sample workpiece 12, in this case a compressor impeller with peripherally formed blades 12a, is produced from an electrically conductive material which is available at low cost using a conventional cutting shaping method. For the sake of simplicity is in the FIGS. 1 to 8 only one part of the tool or of the workpiece is shown with three blades 12a each.

Subsequently, the pattern workpiece 12 (12a) of conductive material is attached to the electrode holder 9, while on the workbench 5 located thereunder, an electrode blank 13 (blank made of an electrode material, for example, brass) is held (see FIG. Fig. 1 ).

In the subsequent step 2, the now as an electrode (pattern electrode) serving, in linear vibrations Z _osz staggered pattern workpiece 12, that is, the individual blades 12a, while circular vibrating C _osz of the electrode blank 13 and gradual vertical type Zvor and zirkularem feed C prior to the Sample workpiece under electrochemical material removal into the electrode blank 13 is lowered ( Fig. 2 ).

In the next step 3 according to Fig. 3 In the recesses 14 of the electrode blank 13, the negative shape of the pressure side 15 of the blades 12a of the pattern workpiece 12 is first formed by _generating a circular _vibration C _osz and at the same time a horizontal rotational feed movement of the electrode blank 13 in the drawing to the left.

According to Fig. 4 In step 4, the electrode _blank 13 _is moved to the right with continuous circular _oscillation C _{osz in} accordance with the feed movement C, in order to form in the recesses 14 of the electrode _blank 13 the negative side of the suction side 16 of the blades 12a.

In Fig. 5 For example, the new electrode or working electrode 13 'produced from the electrode blank 13 in the preceding steps 1 to 4 is reproduced for a series production of components whose shape corresponds to the above-mentioned sample workpiece 12, according to the PEM method. The working electrode 13 'is not the perfect negative of the sample workpiece 12 in terms of wall thickness, but in terms of the shape of the pressure and suction sides of the blades 12a.

For mass production, the working electrode 13 'on the electrode holder 9 of the in Fig. 9 attached device, and on the work table 5, a blank 17 is clamped to which the desired shape is to be formed in order to produce by electrochemical removal, for example, compressor discs (blisk discs) from an aviation-suitable or schwerzerspanbaren material easily, quickly and accurately.

According to Fig. 6 be with simultaneous linear oscillation Z _osz the working electrode 13 '(electrode _holder 9) and circular _oscillation C _{osz of} the blank 17 ( _worktable 5) and gradual vertical feed Z _before and C _before the working electrode 13 (electrode holder 9) in a fifth step on the blank 17 first Webs shaped as a precursor of the blades. In two further process _steps (6 and 7), the blades 17a are then retained while maintaining the circular _oscillation C _{osz of} the blank 17, and at gradual rotational feed C in _{front of} the blank 17, first in one direction ( Fig. 7 , Step 6) and then in the opposite direction of rotation ( Fig. 8 , Step 7) to its exact wall thickness and three-dimensional arched shape finished.

For mass production, the in the FIGS. 5 to 8 illustrated process steps 5 to 7 repeated as often as desired to produce in this way with respect to the known milling process significantly reduced time and effort compressor disks (blisk disks) in highest manufacturing accuracy.

After the above based on the FIGS. 1 to 8 described method and the corresponding device according to FIG. 9 the essential feature of which is that linear motion is superimposed on linear oscillation, circular motion and rotational feed motion in one and the other direction, blade rings or sections of these or individual blades, for example replaced or repaired blades, by electrochemical Abtragen after the PEM process in a narrow tolerance range formed or finished. The method described in the exemplary embodiment is, of course, also suitable for other applications for the production of complicated-shaped components for which the electrochemical machining has hitherto not been usable due to the workpiece areas that can not be reached for the electrode. In certain applications (workpiece shapes), the linear oscillation can also be carried out separately from the circular oscillation, in that the electrode first penetrates exclusively by linear oscillation into the workpiece and then further shaped exclusively by circular oscillation the workpiece in the direction perpendicular to the linear processing. Similarly, the invention is not limited to the embodiment with respect to the assignment of the respective oscillatory and feed movements. For example The linear and circular oscillation and / or the linear and circular feed can also be performed exclusively by the electrode.

Fig. 10 shows a variant of the in Fig. 9 in which, in order to be able to form individual blades on a paddle wheel or of a drum formed of a plurality of juxtaposed paddle wheels or to be able to repair a single paddle, the tool carriage 8 can be mounted on the machine portal 3 in both the X direction and in the Y-direction is movable and the circular _oscillation C _osz and the circular _feed C in _front of a horizontal axis in which the drum to be processed is arranged take place.

LIST OF REFERENCE NUMBERS

1

base

2

Sidewall

3

machines portal

4

machine housing

5

Workpiece holder (work table)

6

Torsional vibration drive (1st drive)

7

Rotary feed drive (2nd drive)

8th

tool slide

9

electrode holder

10

3-4. drive

12

Sample workpiece

12a

shovel

13

electrode blank

13 '

Working electrode (workpiece negative electrode)

14

Recess in 13

15

Negative form v. Blade pressure side

16

Negative form v. blade suction

17

blank

17a

shovel

18

Stege v. 13 '

Arrow C _osz

circular oscillation

Arrow C _before

circular feed

Arrow Z _osz

linear vibration

Arrow Z in _front

linear feed

Arrow X

hor. Slide feed X-axis

Arrow Y

hor. Slide feed Y-axis

Claims (5)

1. Method for the forming of components of complex shape, in particular turbomachine rotor wheels which constitute a single piece with the blading, by electrochemical material removal, in which, in the presence of an electrolyte, a linear oscillation (Z_osz) of an electrode (12, 13') or of a workpiece or blank (13, 17) to be machined is performed relative to each other, with simultaneous, gradual linear feed (Z_vor), characterized in that the linear oscillation and feed (Z_osz, Z_vor) is superimposed by a circular oscillation (C_osz) and a circular feed (C_vor).
2. Method in accordance with Claim 1, characterized in that the linear oscillation and the linear feed and/or the circular oscillation and the circular feed are performed by the electrode (12, 13') and/or the workpiece/blank (13, 17) to be machined.
3. Method in accordance with Claim 1, characterized in that a negative of the workpiece or workpiece section to be produced is initially made by means of a sample workpiece (12) serving as electrode, said negative being used as working electrode (13') in series production, with said negative first being machined into the blank (17) in synchronous linear and circular oscillation and with at least one of the side surfaces then being further formed by circular oscillation.
4. Method in accordance with Claim 1, characterized in that the various machining positions of one and the same workpiece are electrochemically machined synchronously.
5. Method in accordance with Claim 1, characterized in that the various machining positions of one and the same workpiece are electrochemically machined separately.

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